This change introduces integration tests for `linkerd inject`. The tests
perform CLI injection, with and without params, and validates the
output, including annotations.
Also add some known errors in logs to `install_test.go`.
TODO:
- deploy uninjected and injected resources to a default and
auto-injected cluster
- test creation and update
Part of #2459
Signed-off-by: Andrew Seigner <siggy@buoyant.io>